1. Field of the Invention
The present invention relates to a broadcast system and a channel setting method therein.
2. Description of the Related Art
A digital or analog broadcast receiving system, such as a cable modem, a digital TV, an analog TV, and a set-top box, receives a broadcast signal which contains channel information or broadcast information (voice or image information) from a head-end or a broadcasting station.
The broadcast system scans a channel containing the received broadcast signal to obtain broadcast information such as terrestrial broadcast information and satellite broadcast information, and channel information, and stores the obtained channel information so that a user can rapidly select a desired channel.
The broadcast system may provide an automatic channel searching function as a supplemental function.
When the automatic channel searching function is initially set up for a user's convenience, the broadcast system scans channel information received from head-ends and broadcasting stations and stores only channel information, i.e., sets channels, corresponding to broadcast information among the scanned channel information.
Then, the broadcast information received through the set channels is provided in response to a channel UP/DOWN key signal received from a remote controller or a previously set button, so that the user can conveniently watch desired broadcasting.
If the broadcast system does not have the automatic channel searching function, the user has to search through all channels using the remote controller or the previously set button in order to select a desired channel.
The user even has to search through channels which do not have broadcast information, which makes the whole process of searching for a desired channel inefficient and inconvenient.
In Korea, head-ends or broadcasting stations are allocated a broadcasting frequency band of from 54 MHz to 864 MHz, each channel containing broadcast information is allocated a frequency bandwidth of 6 MHz, and a broadcast signal is transmitted through each channel having a frequency band of 6 MHz.
Here, there are a total of 135 frequency bands, i.e., 135 channels for broadcast information, and the broadcast information provided from each head-end or broadcasting station is contained in each allocated channel and then transmitted to the broadcast system.
However, because not all channels are used for broadcasting information, searching through channels having no broadcast information should be skipped, only information about channels having broadcast information should be stored, and broadcast information corresponding to channel information set by the user should be provided to the user.
Thus, there is a need to scan broadcast information received from the head-end or the broadcasting station and set only channel information having broadcast information fast and efficiently.
FIG. 1 shows a location of a center frequency to which a tuner is to be locked in a typical broadcast system.
Referring to FIG. 1, an entire broadcasting frequency band has a bandwidth of 54 MHz to 864 MHz, of which each channel F[n] is allocated a bandwidth of 6 MHz, wherein n is the number of a channel and may be less than or equal to 135.
Generally, the tuner of the broadcast system is locked to the center frequency Fc[n] of a 6 MHz channel n and produces an intermediate frequency (IF) broadcast signal corresponding to the center frequency Fc[n].
When the tuner is locked to a certain frequency band, the broadcast system can receive only the signal broadcast over that frequency band.
The tuner transmits the IF broadcast signal to an IF amplifier which amplifies the received broadcast signal by a prescribed level and transmits it to a demodulator which demodulates the received IF broadcast signal.
Channel information is obtained by a demodulation procedure, the demodulator stores the obtained channel information under the control of a controller, and the tuner proceeds to lock to the center frequency Fc[n+1] of the next channel.
In the above-described method, the tuner sequentially locks to each of all 135 channels regardless of whether the channel has broadcast information or not, which is time-consuming and inefficient.
That is, the typical broadcast system employing the automatic channel searching function checks every channel for broadcast information in order to obtain the channel information. Thus, if the time taken to scan one channel is T, the time taken to scan all 135 channels is 135×T.